Preparation of poly alpha, alpha 2,3,5,6-hexafluoro-p-xylylene

ABSTRACT

A method for the preparation of new highly fluorinated pxylylene monomers and polymers which have excellent chemical and thermal properties.

United" States Patent [151 3,694,495 Norris 1 Sept. 26, 1972 [54] PREPARATION OF POLY ALPHA, [58] Field of Search ..260/5 15 A ALPHA 2,3,5,6-HEXAFLUORO-P- XYLYLENE [56] References Cited [72] Inventor: William P. Norris, China Lake, UNITED STATES PATENTS Calif.

- 3,280,180 10/1966 Buxton et al. ..260/5l5 [73] Assignee: The United States of America as represented by the Secretary of the 3,459,794 8/1969 Tamborskl ..260/5l5 Navy Primary Examiner-James A. Patten Filed: 2,1970 Attorney-George J. Rubens, Roy Miller and Victor 21 Appl. No.: 94,539 Muller Related U.S. Application Data [5 7] ABSTRACT Division Of 723,908, April 1968, A method for the preparation of new highly 3,626,031 fluorinated p-xylylene monomers and polymers which have excellent chemical and thermal properties. [52] US. Cl. ..260/5l5 A [5]] Int. Cl ..C07c 63/52 2 Claims, N0 Drawings r PREPARATION OF POLY-ALPHA, ALPHA 2,35,6-

IIEXAFLUORO-P-XYLYLENE REFERENCE TO RELATED APPLICATION v This invention is a division of patent application Ser. No. 723,908, filed in U. S. Patent Office on Apr. 24, 1968 now matured to U.S. Pat. No. 3,626,032.

BACKGROUND OF THE INVENTION This invention relates to a new fluorinated p-xylylene polymer and to the process for the preparation thereof.

The chemicalandithermal stability exhibited by the paraxylylene polymer family has prompted various efforts to prepare new and improved compounds of this group on a simple and practical scale. The present invention provides a new fluorinated p-xylylene polymer 7 which has good thermal stability.

SUMMARY OF THE INVENTION This invention is for poly-' ,a,2,3,5,6-hexafluoro-pxylylene and the synthesis thereof. The general purpose of this invention is to provide a new fluorinated p-xylylene polymer which is heat stable to temperature of over 400 C. Another object is toprovide a polymer which is useful as a coating for mirrors, metals, and surfaces which are subject to high temperatures. Other objects, features, and many of the attendant advantages of this invention will become readily appreciated as the same become better understood by reference to the fol-' lowing detailed description.

DESCRIPTION OF THE INVENTION In accordance with the present invention polya,a,2,3,5,6-hexafluoro-p-xylylene, having the following repeating unit, I

is produced by the process which comprises forming a reactive intermediate or precursor, 2,3,5,6,7,7-hexafluoro-p-quinodimethane which has the structural formula The polymer can be readily recovered from the condensation polymerization zone by. any convenient means depending on the particular zone employed. Where a cold surface, such as a condenser, is employed as the polymerization zone the polymer is removed from the wall of the polymerization zone by mechanically stripping it off after simply wetting it with a solvent such as acetone. It is not to be implied that the polymer of this invention has to be removed or recovered from the depositing surface since it is simple and easy to place the surface or substrate to be coated within or as part of the polymerization zone. Small articles of various shapes can be protected or encapsulated with the present polymer and deposition of the polymer on continuously moving surfaces of metal, paper, glass or the like can readily be accomplished within the deposition zone.

The following reaction sequence used for the preparation of this polymer is as follows:

Add 22.6 grams 0.20 mole) of ethyl cyanoacetate to 5.0 grams (0.21 mole) of sodium hydride suspended in milliliters of dimethylformamide keeping the reaction temperature at 25 C. 1': 5. When hydrogen evolution ceases, 23.6 grams (0.10 mole) OF octafluorotoluene is added while maintaining the temperature at 25 C. 5. The reaction mixture is poured into 300 milliliters of ice water and extracted with 100 milliliters of ether. The ether phase is discarded. Next, add 30 milliliters of concentrated hydrochloric acid to the aqueous phase and extract with 3 50 milliliter por-' FF H The yield is 85 percent, b.p. l07-l l3 at 1.5 mm pressure, and m.p. is 48-5 1 C. An elemental analysis gave the following for C I-I F NO Calculated: C 43.78; H 1.84; F 40.40; N 4.26

Found: C 44.08; H 2.08; F= 39.86; N= 4.67

28 grams of the compound formed by the process described hereinbefore, ethyl(4-trifluoromethyl- 2,3,5,6-tetrafluorophenyl)cyanoacetate, was added to 50 milliliters of water, 50 milliliters of acetic acid and milliliters of sulfuric acid and the mixture was heated at reflux for 5 hours. The mixture was poured into 500 milliliters of water and cooled to 5 C. overnight. The solid was filtered off to give 20 grams of a product having a m.p. of 60-70 C. Recrystallization from n-hexane gave 18 grams of (4-trifluoromethyl- 2,3,5,6-tetrafluorophenyl)acetic acid having the structural formula The m.p. is 7780 C. An elemental analysis gave the following for C l- 2 Calculated: C= 39.15; l-l= 1.09; F=48.l7

Found: C=39.04; H= 1.22; F=49.52

About 4.7 grams (0.017 mole) of the (4- trifluoromethyl-2,3,5,-tetrafluorophenyl)acetic acid was suspended in 25 milliliters of water, two drops of phenolphthalein indicator solution was added, then a 50 percent potassium hydroxide solution was added to give a faint pink end point. The water was removed under reduced pressure at 25 C. The dry residue was dissolved in milliliters of acetone, filtered, and heated to boiling. Ethylene dichloride was added to the cloud point. Cooling gave 5.0 grams (93 percent yield) white needles having a melting point of 222 C. The salt was heated at 100 C. for 5 hours at 0.001 mm pressure and the product, potassium (4-trifluoromethyl-2,3,5,6- tetrafluorophenyhacetate having the structural formula F F cmGcmcmx was analyzed with the following results for C H F O K: Calculated: C= 34.40; H= 0.64; F=42.33; K= 12.44

Found: C 34.20; H 0.57; F= 42.37; K= 12.48

2 grams of potassium (4-trifluoromethyl-2,3,5,6- tetrafluorophenyl)acetate, prepared by the method described hereinbefore, was evacuated to a pressure of 0.01 mm and was heated in a 250 C. bath. The monomer, identified as 2,3,5,6,7,7-heXafiuoro-p-quinodimethane, was emitted as a gas which when led through a condenser cooled with Dry Ice formed a thin film which was isolated and characterized as the polymer, poly-a,a,2,3,5,6-hexafluoro-p-xylylene. The film removed by wetting with acetone was 0.04 mm thick, clear, and pliable. An X-ray diffraction pattern on the film dried at l00/0.00l mm showed definite lines indicating crystallinity. The sample polymer was held at 500 C. for 20 minutes and showed a 17 percent weight loss. A difierential thermal analysis under nitrogen shows a small endothermic process starting at 421 C. An elemental analysis was made as follows for sIfiFsh Calculated: C= 45.30; H=0.95; F=53.75

The products formed in the various steps described in the reaction process herein are not only valuable as chemical intermediates or precursors for the synthesis of the high temperature polymer used in coating varithew ayment of any royalties thereon or therefor.

at 18 claime 1s:

1. The composition having the structural formula 2. The composition having the structural formula F F (am-Gotham 

2. The composition having the structural formula 